1. Field of the Invention
The present invention relates to a semiconductor light-emitting device including a semiconductor chip having a pair of electrode films in the same side of a mounting plate, to a method of manufacturing the same, and to a mounting plate used for the method thereof
2. Description of the Related Art
In recent years, semiconductor light-emitting devices including a semiconductor laser device in which a nitride semiconductor such as GaN is employed as a light source for short-wavelength light have been developed. Generally, with the semiconductor laser device utilizing the nitride semiconductor, an n-type layer, an active layer and a p-type layer, which are made of the nitride semiconductor are stacked in sequence on a substrate made of sapphire (Al2O3). Among a pair of electrode films of the semiconductor laser device, a p-side electrode is formed on the p-type layer which is the most upper layer in the semiconductor layer, while an n-type electrode is formed on the n-type layer which is exposed by etching the p-type layer and the active layer. Hence, the substrate, the semiconductor layer, the p-side electrode and the n-side electrode are collectively called a semiconductor chip.
In the semiconductor light-emitting device, the semiconductor chip is mounted on a mounting plate called a submount. The semiconductor chip is mounted on the mounting plate in a state, in which a side of the semiconductor layer is opposed to the mounting plate in order to scatter heat generated in the semiconductor layer effectively. The mounting plate has a pair of lead electrode layers formed in a side where the semiconductor chip is mounted thereon, and a solder film is formed on the lead layers. After mounting the semiconductor chip on the mounting plate, the p-side and the n-side electrodes of the semiconductor chip respectively contact with a pair of the lead electrode layers via the solder film.
However, in the conventional semiconductor light-emitting device, when the semiconductor chip is worn on the submount, the pressed solder film with the p-side and the n-side electrodes of the semiconductor chip is squeezed out to the side of the solder layer. Then, the squeezed-out solder may adhere to a pn junction part of the semiconductor chip, which causes the short circuit failure.
Additionally, the squeezed-out solder may adhere to a vicinity of an ejection part of a laser beam. In such a case, a shape of the laser beam changes, and what""s worse, an optical-power output decreases. If a shape of the laser beam changes as mentioned before, specifically, when this semiconductor light-emitting device is applied to an optical disk apparatus and so on, it leads to less tracking accuracy. On top of that, such decrease of the optical-power output of the laser beam causes increase of heating value, because a large amount of current must be flowed to the semiconductor chip in order to acquire rated output.
The invention has been achieved in consideration of the above problems and its object is to provide a semiconductor light-emitting device capable of preventing the short circuit failure in the pn junction part caused by adhesion of the solder, change of a beam shape, and decrease of an optical-power output and a method of manufacturing the same and a mounting plate.
A method of manufacturing a semiconductor light-emitting device according to the present invention comprises a step of overlaying a first and second electrode films of a semiconductor chip to a predetermined supporting body by using a first solder film and a second solder film, and in the semiconductor chip, a surface of the first electrode film is projected beyond a surface of the second electrode film in a manner that the deformation amount of the second solder film is larger than that of the first solder film.
Other methods of manufacturing semiconductor light-emitting devices according to the present invention comprises a step of overlaying the first and second electrodes to the first and second solder films of a mounting plate. A semiconductor provides a level difference such that a surface of the first electrode is projected beyond that of the second electrode therebetween. A mounting plate provides a level difference such that a surface of the first solder film is projected beyond a surface of the second solder film therebetween, and the level difference in the mounting plate is determined in a manner to be higher than that of the semiconductor chip.
A mounting plate according to the present invention is provided with the supporting body, the first and second solder films formed in the same side of the supporting body. Between the first solder film and the second solder film, a level difference is formed such that the surface of the first solder film is projected beyond that of the second solder film and is higher than that of the semiconductor chip.
A semiconductor light-emitting device according to the present invention comprises the semiconductor chip having the first and second electrodes in the same side of the mounting plate, and the mounting plate having the first and second solder films in the same side of the supporting body. The semiconductor chip includes the level difference such that the surface of the first electrode film is projected beyond that of the second film therebetween. The mounting plate provides the level difference such that the surface of the first solder film is projected beyond that of the second solder film therebetween. The supporting body has a trench formed in an opposite side to the second solder film as sandwiching the first solder film.
Further, another mounting plate according to the present invention has the first and second solder films in the same side of the supporting body and provides the level difference such that the surface of the first solder film is projected beyond that of the second solder film therebetween. The supporting body has a trench formed in an opposite side to the second solder film as sandwiching the first solder film.
Furthermore, another method of manufacturing a semiconductor light-emitting device according to the present invention comprises a step of overlaying the first and second electrodes of the semiconductor chip to the first and second solder films of the mounting plate. The semiconductor chip provides the level difference such that the surface of the first electrode is projected beyond that of the second electrode. The mounting plate provides the level difference such that the surface of the first solder film is projected beyond that of the second solder film. An outline of the first solder film in a contact surface between the first electrode and the first solder film is positioned inwardly from an outline of the first electrode in the contact surface, at least in a specific direction.
In the method of manufacturing a semiconductor light-emitting device, another method of manufacturing the semiconductor light-emitting device, or the mounting plate according to the present invention, when the semiconductor chip is overlaid to the mounting plate, the first electrode contacts with the first solder film after the second electrode film contacts with the second solder film. Accordingly, even if solder of the second solder film is squeezed out, solder of the first solder film is prevented squeezing out. The pn junction part of the semiconductor chip is generally disposed in a side of the first electrode having an amount of projection larger than the other; hence, the solder may be prevented from adhering to the pn junction part.
In the semiconductor light-emitting device or other mounting plates according to the present invention, the supporting body has the trench formed in the opposite side of the second solder film as sandwiching the first solder film. In case that the solder of the first solder film is squeezed out, the solder flows into the trench, which prevents the solder from adhering to the pn junction part. (The pn junction part is generally disposed in the vicinity of the first electrode film.)
In the other method of manufacturing a semiconductor light-emitting device, an outline of the first solder film in contact surfaces of the first electrode film and the first solder film is positioned inwardly from an outline of the first electrode film (at least in a specific direction). Hence, even the first solder film is applied to pressure, the solder is hardly squeezed out from the out side of the outline of the first electrode film. Accordingly, the solder film is prevented from adhering to the pn junction part of the semiconductor chip.